#include <stdio.h>

int main(void)
{
	float x;
	printf ("注：结束程序请按Ctrl + C\n");
	
	do {
		printf("请输入学生成绩");
		scanf("%f", &x);
		
		if (x < 60){ //X < 60
			printf("没有通过！这样可不行！\n");
		}else if(x < 70){ //60 <= X < 70
			printf("及格，得努力！\n");
		}else if(x < 80){ //70 <= X < 80
			printf("还可以，加油！\n");
		}else if(x < 90){ //80 <= X < 90
			printf("不错，继续！\n");
		}else if(x <= 100 ){ //90 <= X <= 100
			printf("很好！\n");
		}else{ //程序兜底
			printf("未知错误！\n");
		}
	}while (1);
	
	return 0;
}
